This invention relates generally to wear-resistant materials and articles, and more particularly to amorphous materials and articles having excellent wear resistance.
Wear is a problem of enormous significance, since even by conservative estimates billions of dollars are lost each year as a result of wear. The costs of wear arise directly through the need to replace worn articles such as machine components, and also indirectly through reduced machinery efficiency, loss of critical tolerances in machinery, breakdowns caused by wear and down time necessitated by the need to inspect and replace worn components. Thus, the economic loss due to wear is not simply proportional to the amount of material worn away.
Wear may occur by a variety of mechanisms, and several different schemes of classifying wear processes have been proposed. According to one such classification scheme, in a particular situation wear may occur by abrasion, adhesion, erosion, fretting, or chemical mechanisms, or by combinations of two or more such mechanisms. As a result of the several mechanisms and many types of materials subjected to wear, no generally satisfactory method for predicting the wear resistance of materials or articles has been found. In some environments and applications, hard materials such as ceramics have been found to be wear-resistant, while in other environments and applications soft materials such as rubber are favored.
Wear of articles is generally controlled by proper design, by selection of wear-resistant materials and by protection of materials in use. In the design approach, wear is minimized or avoided by minimizing the exposure of susceptible materials to a wear-inducing environment. Materials are protected in use by various means such as lubrication of wearing components. In the material selection approach, wear-resistant materials are developed, tested and selected for use in wear-inducing environments such as earth moving or drilling, where the exposure cannot be avoided by proper design.
Regardless of the mechanism of wear, wear is generally a phenomenon occurring at or near a surface rather than in the interior of the material. A wide variety of techniques have been developed for improving the wear resistance of surfaces, including heat treatments, surface composition or hardness treatments, and the use of wear-resistant coatings or hard facings. Together with the development of more highly wear-resistant bulk materials, these techniques have resulted in improved wear resistance of articles such as those used in machine components. However, the most wear-resistant materials have serious shortcomings in specific applications. Rubber has a low strength and cannot be used at high temperatures. Hard-facing alloys typically are brittle or have little ductility, limiting their means of application and leading to cracking and spalling of the coating in use. Popular bulk wear-resistant alloys such as tungsten carbide-cobalt (WC-Co) powder materials lack tensile strength and ductility, are often not readily fabricated as coatings or hard facings, and are susceptible to flaking and spalling during use. Materials are often required for use in corrosive environments, and many common wear-resistant materials lack the combination of corrosion and wear resistance.
Thus, there continues to be a need for improved materials for use in resisting or protecting against wear. In particular, there exists a present need for materials having high wear resistance, good tensile and compressive strength, ductility, corrosion resistance and fabricability. The present invention fulfills this need, and further provides related advantages.